New Technology and Basic Study on the Direet Preparation of PbO Powder from Galena by Selective Leaching Technology
|School||Changsha University of Science and Technology|
|Keywords||galena leaching ozone hydrogen peroxide superfines|
Production of lead has a very long history,From rough processing of lead to deep processing reflects the crystallization of the mankind wisdom, From lead-containing raw material to the senior lead materials,which Must undergo through multiple high-temperature and energy-intensive process. Owing to the emission of SO2 and lead smoke dust as well as lead filled dust during processes of lead metallurgy and electrolysis, there is serious pollution to environment,and that hydrometallurgy is still in the primary stage. Under the current pressures of strict environmental regulations, it is time to seek other methods to produce lead materials for the developing economy and sustainable society. In this paper,a new approach to direct produce lead monoxide from galena concentrates has been proposed.Today, the lead-consuming of lead acid batteries account that of total for 70% in our country,PbO powders as an active material of lead acid batteries are prepared from galena concentrates through a three-step method,viz leaching-selective purification-chemical synthesized. This process without pollution not only simplifies the traditional process of the production of PbO, but enhances the efficiency of processing lead mineral resources. In this thesis,two sorts of leaching systems both galena-pyrolusite-hydrochloric acid system and ozone-hydrogen peroxide- hydrochloric acid system were investigated respectively.The dissolution of galena concentrate in HCl and NaCl electrolyte was investigated,pyrolusite was used as oxidizing agent. Studying the influence of sodium chloride concentration and react time and hydrochloric acid concentration on the leaching rate. The results show that the dissolution rate increases with the increase in liquid-to-solid ratio, oxidizing agent dosage, HCl concentration, NaCl concentration and temperature. When the liquid-to-solid ratio is 10:1, stirring speed is 500 r/min, concentration of NaCl is 300 g/L at temperature 80℃, the leaching efficiency of galena concentrate will reach 90% in 60 min. Galena concentrate can be oxidized indirectly by pyrolusite. High purified 96% lead chloride generated. On the base of two-ores method, a study on O3- H2O2-HCl leaching was conducted, hydrometallurgical leaching of galena, especially oxidation leaching in aqueous solution, has been attracting worldwide attention. Based on literature searched and read, a craft which galena leached via ferric chloride combine with a strong oxidant resulted from peroxone was proposed. Peroxone namely ozone react with hydrogen peroxide in low temperature（90℃） in the presence of diluted hydrochloric acid. It demonstrated that multiple oxidants work together can decrease the consumption of ozone sharply. After optimizing experiments, an satisfactory recovery of 96.7% Pb and purity of 99. 4% lead chloride was provided in optimal conditions that particle size -0.075 mm, concentration of hydrogen acid 0.3mol/L, concentration of hydrogen peroxide 6.66g/L, leaching time of 3.5 h. Constant temperature water bath 90℃was needed. Technological process cooling-crystallization- filtration have the function of removal of impurity.Preparation of electronic grade PbO powder from PbCl2result from leaching mentioned above were affected by many factors such as material rate, reaction temperature reaction time and ultrasonic frequency. PbO prepared in this thesis is rhombic. There is no other product from X-ray diffraction analysis with the average particle size of PbO of 80nm at the scale of nanometer, and it is flaky powder from scanning electron microscope spectrum. Intermediate samples, including PbOx, Pb3O4,α-PbO andβ-PbO, can exist stably in the process of calcining the precursor, a mixture of lead carbonate and basic lead carbonate, at different temperature.